1. Field of the Invention
The present invention relates to semiconductor substrates, and more particularly, relates to silicon substrates having nanostructures.
2. Description of Related Art
Anti-reflection layers are typically employed above silicon layers of optoelectronics, such as solar cells, detectors, and photodiodes, to maximize the amount of light absorbed in the silicon layers. Increasingly greater amounts of light absorbed of course tend to promote more efficient optoelectronics. As evidenced by the reflective index of silicon being a relatively high 3.5 to 4, the reflectivity of silicon layers is more than 30%; therefore, anti-reflection layers can be highly beneficial for retarding large amounts of light from being reflected back from the silicon surface. In particular implementations, anti-reflection layers typically employ anti-reflection films or various nanostructures textured on silicon surfaces to reduce the light reflected off the silicon surface.
The various nanostructures, such as nanowires, nanoholes, nanocolumns, nanoneedles, and the like, reduce reflection losses by increasing the light path whereby the light strikes the silicon multiple times, and by decreasing the reflective index whereby more light is confined within the silicon. However, nanostructures having too large of a surface area can cause the carrier recombination to be increased, thus lowering the efficiency of the optoelectronics.
Therefore, a demand exists in the prior art for silicon substrates having nanostructures that maximize the amount of light absorbed in the silicon layer while not lowering the efficiency of the optoelectronics. Another demand is for the nanostructures to provide excellent anti-reflection performance over a wide wavelength range, preferably, in the substantially whole wavelength range comprising the wavelengths of ultraviolet, infrared, and visible light.
Accordingly, it would be advantageous to provide silicon substrates having nanostructures, and forming methods and applications thereof, that can satisfy the above demands and resolve the problems of the prior art.